Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)
Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS)
Principles of Operation
The Restraints Control Module (RCM) continuously receives/monitors all inputs from the following Supplemental Restraint System (SRS) components.
- LH and RH front impact severity sensors
- Driver and passenger front door side impact sensors
- Driver and passenger second row side impact sensors
- Safety belt buckle switches (driver and passenger)
- Driver seat track position sensor
- Occupant Classification System Module (OCSM)
If the RCM (Restraints Control Module) detects sudden vehicle deceleration and/or lateral deceleration based on all the information received from all sensors and switches and determines that deployment is required, the RCM (Restraints Control Module) sends voltage and current to deploy the appropriate SRS (Supplemental Restraint System) components.
The RCM (Restraints Control Module) contains an internal sensor that detects vehicle rollover angles. If the RCM (Restraints Control Module) determines that a rollover condition exists and deployment is required, the RCM (Restraints Control Module) deploys the applicable SRS (Supplemental Restraint System) components.
During a frontal or side crash, the RCM (Restraints Control Module) can deploy the following SRS (Supplemental Restraint System) components, based on crash severity and sensor input.
- Safety belt retractor pretensioner(s)
- Seat side air bag(s)
- Safety Canopy(R)
- Driver and passenger dual-stage air bag(s) (one or both stages)
The fact that the safety belt pretensioners, Safety Canopy(R) or air bags did not activate for both front seat occupants in a crash does not indicate that something is wrong with the system.
The RCM (Restraints Control Module) carries out a self-test of the SRS (Supplemental Restraint System) during each startup. If a SRS (Supplemental Restraint System) fault exists, the air bag warning indicator illuminates and remains illuminated for the rest of the ignition cycle. In addition to the self-test at start up, the RCM (Restraints Control Module) continuously monitors all of its SRS (Supplemental Restraint System) components and circuitry for correct operation.
Air Bag Warning Indicator
The air bag warning indicator:
- is located in the Instrument Panel Cluster (IPC) and proves out by lighting for 6 seconds and then turn off.
- flashes and/or illuminates based on the message the IPC (Instrument Panel Cluster) receives from the RCM (Restraints Control Module).
- illuminates if the IPC (Instrument Panel Cluster) does not receive a message from the RCM (Restraints Control Module).
Air Bag Module Second Stage Deployment Check
Because the driver and passenger front air bags each have 2 deployment stages, it is possible that Stage 1 has deployed and Stage 2 has not.
If a front air bag module has deployed, it is mandatory that the front air bag module be remotely deployed using the appropriate air bag disposal procedure.
- For information on driver air bag module and/or passenger air bag module remote deployment, refer to Pyrotechnic Device Disposal Service and Repair.
Clockspring
The clockspring allows for continuous electrical connections between the driver air bag module and the RCM (Restraints Control Module) when the steering wheel is turned.
Driver Air Bag Module
The driver air bag module is a dual-stage air bag, upon receiving a flow of current from the RCM (Restraints Control Module), deploying at 1 of 2 different rates depending upon vehicle impact severity and impact sensor input.
High Speed Controller Area Network (HS-CAN)
This vehicle utilizes a communication system called a High Speed Controller Area Network (HS-CAN). The RCM (Restraints Control Module) communicates with various modules for required information about the vehicle. for information about the HS-CAN (High Speed Controller Area Network).
Occupant Classification System (OCS)
The Occupant Classification System (OCS) is found only on the front passenger seat. The OCS (Occupant Classification System) classifies the size of the front passenger seat occupant and provides this information to the RCM (Restraints Control Module). The RCM (Restraints Control Module) uses this information (and other inputs) in determining the deployment strategy of the passenger air bag and pretensioner. The OCS (Occupant Classification System) has 2 weight sensor bolts that are mounted to the inboard rail of the seat track and are only serviced with the seat track assembly. The OCSM (Occupant Classification System Module) is mounted to the electrical bracket underneath the seat cushion pan and can be serviced separately from the seat track assembly.
The OCS (Occupant Classification System) is also used for operation of the passenger Belt-Minder(R). For information on the passenger Belt-Minder(R) feature, refer to Seat Belt Systems. To deactivate or reactivate the passenger Belt-Minder(R) feature, refer to Instrument Panel, Gauges and Warning Indicators or the Owner's Literature.
Belt Tension Sensor (BTS)
The Belt Tension Sensor (BTS) :
- is a 3-wire Hall-effect sensor located at the safety belt anchor point and is part of the front passenger safety belt and retractor assembly.
- is used in conjunction with the OCS (Occupant Classification System).
The BTS (Belt Tension Sensor) is used by the OCS (Occupant Classification System) to identify the presence of a child safety seat on the front passenger seat. The BTS (Belt Tension Sensor) senses the tension on the safety belt assembly then provides an output to the OCSM (Occupant Classification System Module), indicating that the safety belt assembly is cinched. After sensing the weight applied to the seat by the occupant and using the BTS (Belt Tension Sensor) input, the OCSM (Occupant Classification System Module) determines how the occupant should be classified and communicates this information to the RCM (Restraints Control Module). If the occupant is classified as a child, the RCM (Restraints Control Module) automatically deactivates the passenger air bag module and illuminates the Passenger Air Bag Deactivation (PAD) indicator.
Passenger Air Bag Deactivation (PAD) Indicator
The PAD (Passenger Air Bag Deactivation) indicator is a visual indicator used to inform the front seat occupants of the front passenger air bag state. The PAD (Passenger Air Bag Deactivation) indicator (part of the hazard/traction control switch assembly) is located in the instrument panel visible to each front seat occupant.
The RCM (Restraints Control Module) controls the state of the PAD (Passenger Air Bag Deactivation) indicator through a direct hard-wired connection, based on information provided by the OCSM (Occupant Classification System Module). The PAD (Passenger Air Bag Deactivation) indicator is lit to indicate the front passenger air bag module is disabled. An exemption to this is when the front passenger seat is determined to be empty, and therefore indication of a deactivated passenger air bag module is not necessary. In all other cases, the PAD (Passenger Air Bag Deactivation) indicator is unlit when the passenger air bag module is enabled.
The RCM (Restraints Control Module) briefly activates the PAD (Passenger Air Bag Deactivation) indicator to prove-out the indicator function and verify to the front occupants correct functional operation of the PAD (Passenger Air Bag Deactivation) indicator.
The following table indicates the passenger air bag status and the PAD (Passenger Air Bag Deactivation) indicator status based the size of the front passenger occupant.
Passenger Air Bag and Passenger Air Bag Deactivation (PAD) Indicator Status
Passenger Air Bag Module
The passenger air bag module is a dual-stage air bag, deploying at 1 of 2 different rates depending upon vehicle impact severity and sensor input.
Restraints Control Module (RCM)
WARNING: Do not handle, move or change the original horizontal mounting position of the restraints control module (RCM) while the RCM is connected and the ignition switch is ON. Failure to follow this instruction may result in the accidental deployment of the Safety Canopy(R) and cause serious personal injury or death.
WARNING: If a vehicle has been in a crash, inspect the restraints control module (RCM) and the impact sensor (if equipped) mounting areas for deformation. If damaged, restore the mounting areas to the original production configuration. A new RCM and sensors must be installed whether or not the air bags have deployed. Failure to follow these instructions may result in serious personal injury or death in a crash.
NOTE: This vehicle is equipped with the SYNC(R) feature which contains the 911 assist option. Refer to the Owner's Literature.
The RCM (Restraints Control Module) carries out the following functions:
- Deploys the air bag(s)/Safety Canopy(R) in the event of a deployable crash
- Activates the driver and passenger retractor pretensioner(s) to control the tension of the driver and passenger safety belts in the event of a deployable crash
- Monitors the SRS (Supplemental Restraint System) for faults
- Sends a message to the IPC (Instrument Panel Cluster) to illuminate the air bag warning indicator if a fault is detected
- Communicates through the Data Link Connector (DLC) the current or historical DTCs
The RCM (Restraints Control Module) monitors the SRS (Supplemental Restraint System) for possible faults. If a fault is detected, the RCM (Restraints Control Module) requests the IPC (Instrument Panel Cluster) to illuminate the air bag warning indicator. When the ignition is turned OFF and then ON, the IPC (Instrument Panel Cluster) proves out the air bag warning indicator by lighting for 6 seconds. If no faults are detected by the RCM (Restraints Control Module), the IPC (Instrument Panel Cluster) turns the air bag warning indicator off and it remains off. If the RCM (Restraints Control Module) detects a fault, it sends a message to the IPC (Instrument Panel Cluster) to turn the air bag warning indicator on and it remains on for the rest of the ignition cycle. If the RCM (Restraints Control Module) requests illumination of the air bag warning indicator and the air bag warning indicator does not function, the IPC (Instrument Panel Cluster) automatically activates an audible chime. The chime is a series of 5 sets of 5 tone bursts. If the chime is heard, the SRS (Supplemental Restraint System) and the air bag warning indicator require repair.
The RCM (Restraints Control Module) includes a backup power supply. This feature provides sufficient backup power to deploy the air bags in the event that the ignition circuit is lost or damaged during impact. The backup power supply depletes its stored energy approximately one minute after power and/or ground is removed from the RCM (Restraints Control Module).
Post Crash Alert Function
The post crash alert is a function controlled by the Body Control Module (BCM). If the RCM (Restraints Control Module) determines that an impact of a pre-determined severity (the air bags may or may not be deployed) has occurred, the RCM (Restraints Control Module) sends a message to the BCM (Body Control Module) over the High Speed Controller Area Network (HS-CAN) and the post crash alert function is activated. The post-crash alert function activates the hazard lamp function and cycles the horn on 3 times, then off for 4 seconds, and repeats this cycle until the battery is discharged or the function is turned off. The post crash alert function can be turned off by:
- pressing the hazard flasher lamp switch (which may need to be pressed more than once).
- pressing the Remote Keyless Entry (RKE) transmitter UNLOCK button.
- pressing the RKE (Remote Keyless Entry) transmitter PANIC button.
Safety Belt Buckle Switches
The safety belt buckle switches indicate to the RCM (Restraints Control Module) whether the safety belts are buckled or unbuckled.
The RCM (Restraints Control Module) also communicates the driver safety belt buckle switch status to the IPC (Instrument Panel Cluster), which monitors the information to control the safety belt warning indicator. For information on the safety belt warning indicator, refer to Instrument Panel, Gauges and Warning Indicators.
Safety Belt Retractor Pretensioner
Safety belt retractor pretensioners control the tension of the driver and passenger safety belts in the event of a deployable collision.
Safety Canopy(R) Module
WARNING: Anytime the Safety Canopy(R) or side air curtain module has deployed, a new headliner and new A-, B- and C-pillar upper trim panels and attaching hardware must be installed. Remove any other damaged components and hardware and install new components and hardware as needed. Failure to follow these instructions may result in the Safety Canopy(R) or side air curtain module deploying incorrectly and increases the risk of serious personal injury or death in a crash.
NOTE: The Safety Canopy(R) modules are NOT interchangeable. If installing a new Safety Canopy(R) module, the correct Safety Canopy(R) module MUST be installed for the vehicle application.
The Safety Canopy(R) module:
- is mounted above the headliner.
- attaches from the A-pillar frame to the B-pillar or C-pillar frame.
Seat Track Position Sensor
The seat track position sensor indicates the position of the driver seat along the seat track to the RCM (Restraints Control Module). The sensor detects the presence of a shunt bracket on the track, indicating that the seat has moved forward beyond a certain point of adjustment. The RCM (Restraints Control Module) uses seat track position sensor information to determine the deployment rate of the dual-stage driver air bag module.
Secondary Air Bag Warning (Chime)
The secondary air bag warning chime is an audible chime located in and controlled by the IPC (Instrument Panel Cluster). If a fault is detected with the air bag warning indicator, a DTC is stored in memory of the IPC (Instrument Panel Cluster). Upon receiving the message from the RCM (Restraints Control Module) that a SRS (Supplemental Restraint System) fault has been detected, the IPC (Instrument Panel Cluster) sounds the secondary air bag warning chime in a pattern of 5 sets of 5 beeps.
Impact Sensor
For this vehicle line, the SRS (Supplemental Restraint System) uses up to 6 satellite sensors in addition to the RCM (Restraints Control Module). The RCM (Restraints Control Module) is mounted to the center tunnel beneath the console (if equipped) or front center seat. All vehicles have 2 front impact severity sensors located in the front of the vehicle, mounted on the radiator support. The first row impact sensors (side restraints sensor 1) are mounted in each of the front doors behind the trim panel, the second row impact sensors (side restraints sensor 2, Crew Cab and SuperCab) are located on each C-pillar. The driver/passenger front door side impact sensor are pressure sensors and are not interchangeable with other sensors on the vehicle. Mounting orientation is critical for correct operation of all impact sensors.
Seat Side Air Bag Module
The side air bag module:
- deploys upon receiving a flow of current from the RCM (Restraints Control Module), initiated by the side restraints sensor and internal RCM (Restraints Control Module) circuitry.
- is mounted in the seat backrest.
- is used in conjunction with a Safety Canopy(R) module.